Maturation and Assembly Stages of IMPDH-Cytoophidia Induced by IMPDH Inhibition

Inosine-5'-monophosphate dehydrogenase (IMPDH) serves as a key regulatory enzyme, catalyzing a crucial step in the de novo synthesis of guanine nucleotides. This enzyme plays a pivotal role in various cellular functions, including proliferation, differentiation, homeostasis, and metabolism. IMPDH has the unique ability to form protein polymer fibers known as IMPDH cytoophidia. These natural biological structures are integral to purine metabolism and play a significant role in regulating changes within the cellular environment. Utilizing advanced techniques such as immunofluorescence microscopy and Western blot analysis, we have demonstrated that ribavirin (RBV) exhibits remarkable efficacy in inducing time-dependent cytoophidia formation when compared to other IMPDH inhibitors. Our observations reveal that small filaments progressively aggregate into larger secondary structures, reaching their peak formation at 12 hours. Subsequently, the structures begin to decrease by 24 hours, and ringlike formations dominate the cellular landscape at a remarkable 62% incidence. These findings suggest a complex and dynamic process of cytoophidia maturation in response to prolonged and time-dependent IMPDH inhibition. This process underscores the sequential emergence and development of secondary structures that surpass the conventional ring-rod configuration. Our study provides valuable insights into the mechanisms underlying cytoophidia formation and their potential implications for cellular regulation and metabolism.